diff --git a/src/channel.c b/src/channel.c
index d654dc0..1363ee9 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -5856,7 +5856,7 @@
     curwin->w_cursor.lnum = lnum + 1;
     curwin->w_cursor.col = 0;
 
-    if (curbuf->b_prompt_callback == NULL)
+    if (curbuf->b_prompt_callback == NULL || *curbuf->b_prompt_callback == NUL)
 	return;
     text = ml_get(lnum);
     prompt = prompt_text();
@@ -5874,4 +5874,28 @@
     clear_tv(&rettv);
 }
 
+/*
+ * Return TRUE when the interrupt callback was invoked.
+ */
+    int
+invoke_prompt_interrupt(void)
+{
+    typval_T	rettv;
+    int		dummy;
+    typval_T	argv[1];
+
+    if (curbuf->b_prompt_interrupt == NULL
+					|| *curbuf->b_prompt_interrupt == NUL)
+	return FALSE;
+    argv[0].v_type = VAR_UNKNOWN;
+
+    got_int = FALSE; // don't skip executing commands
+    call_func(curbuf->b_prompt_interrupt,
+	      (int)STRLEN(curbuf->b_prompt_interrupt),
+	      &rettv, 0, argv, NULL, 0L, 0L, &dummy, TRUE,
+	      curbuf->b_prompt_int_partial, NULL);
+    clear_tv(&rettv);
+    return TRUE;
+}
+
 #endif /* FEAT_JOB_CHANNEL */